The invention relates to an actuator employing piezoelectric elements and more particularly to an actuator apparatus for magnifying the piezoelectric effect.
Referring to FIG. 2, one conventional type of actuator employing a piezoelectric element will be explained. Numeral 21 denotes a "U" shaped panel frame providing a longer arm 21l and a shorter arm 21s. Frame 21 provides fixing holes 21h. Action levers 22 and 23 are connected forming a "J" shape, and are extended from the longer arm 21l via thin hinge portions 24 and 25, respectively.
A laminated piezoelectric element 26 has one end fixed to the shorter arm 21s and another end fixed to the action lever 22 via a thin hinge portion 27 which is extended from the action lever 22. Numeral 28 denotes a wire having one end fixed to the end of action lever 23.
In construction, the above-described actuator may be press-formed as one unit, except for its piezoelectric element 26 and the wire 28.
With the above-described conventional actuator (FIG. 2), when piezoelectric element 26 expands, action lever 22 tends to rotate clockwise keeping the hinge 24 as a fulcrum. Due to this rotation, the action lever 23 is rotated clockwise keeping the hinge 25 as a fulcrum, and the wire 28 moves upwardly. Displacement D of the wire 28 is expressed by the following formula: ##EQU1## .DELTA.l=the displacement of the piezoelectric element; a=the distance between hinge 24 and hinge 27;
b=the distance between hinge 24 and hinge 25; PA1 c=the distance from hinge 25 to supporting end of the action lever 23; and PA1 d=the distance from the hinge 25 to the wire 28.
For example, if .DELTA.l=10 .mu.m (1 .mu.m=0.001 mm), a=5 mm, b=20 mm, c=5 mm, and d=40 mm, the displacement D of the wire 28 becomes 320 .mu.m. Thus, the actuator of FIG. 2, having the given measurements, has a "magnifying power" of 32.
Since the action levers 22, 23 are extended from the longer arm 21l via the thin hinge portions (fulcrums) 24, 25 respectively, to get increased magnifying power from the piezoelectric effect of element 26, actuators of the type illustrated in FIG. 2 needed to have a wider size as a whole, and accordingly such actuators became more bulky in size and heavier in weight.
It is therefore an object of the invention to obtain an actuator adaptable for increased power while maintaining a compact size and a light weight.